This long-term program of research aims to elucidate deviate neurophysio processes associated with psychiatric disorders and to develop evoked potential (EP) and EEG indicators as objective aids to diagnosis and monitoring of treatments. Numerous EP and EEG differences between clinical groups have been demonstrated, but most are not sufficiently precise for immediate clinical application. The proposed research Involves two main lines of inquiry aimed at: 1. increasing the specificity of clinical differentiation through subtyping; 2. elucidating some basic netiropilysiological aspects of somatosensory EPs (SEPS) that relate to previously found correlates of psychopathology. Both approaches include evaluation of functional topography by "brain mapping" and also determination of effects of psychoactive drugs. 1. in . A series of subtyping hypotheses will be tested, utilizing available data for about 800 subjects. For example, with respect to predominance of negative or positive symptoms in schizophrenics, it is predieted that SEPs of positive symptom patients will contain higher amplitude early components than those of negative symptom patients. 2. SEP recovery functions. Our previous studies showed early SEP recovery to be deviant in many psychiatric disorders, but the SEPs that were measured represented a mixture of precentral and postcentral events that now can be separately identified and measured by means of topographic and recovery function methods. Recovery function measurements will focus on 7 components from 15 to 60 msec poststimulus; probable cortical generators have been identified for these components. Eight interstimulus intervals, from 0 to 90 msec will be used. The recovery measures will permit evaluation of dynamic - physiological properties of several cortical areas; these will be correlated with psychopathologic criteria. Repeat studies will be conducted to determine whether SEP recovery deviations in the major psychoses vary in relation to changes in clinical state.